Fix Mac OS X buildbot

packet-cp2179.c:719: warning: declaration of 'index' shadows a global declaration

Change-Id: Ic622b4f90f9816a43bc62bcb3ce438fbfab3d8a5
Reviewed-on: https://code.wireshark.org/review/3983
Reviewed-by: Alexis La Goutte <alexis.lagoutte@gmail.com>